CRRT (Continuous Renal Replacement Therapy)

CRRT (Continuous Renal Replacement Therapy)

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Provides renal support to patients. Usually veno-venous, but arterio-venous exists too (not covered here).

Mechanisms and types

Solute removal mechanisms:

• Diffusion
  • Accomplished by passive movement of solute across a membrane
  • Efficient clearance of low-molecular-weight solutes (< 500-1,500 Daltons)
  • Clearance decreases with increasing molecular weight of solute
• Convection
  • Accomplished by active movement of solute (due to a pressure gradient) across a membrane
  • Limited primarily by size of pores in membrane
  • Clearance of different size of solute similar until the size of the solute reaches with size of the pores
  • Overall CVVH with higher clearance rate than CVVHD for solutes 1,000 to 20,000 Daltons

Main types (see figure 1 for diagrams):

• SCUF (Slow continuous ultrafiltration)
  • Convection
  • Mainly fluid removal
• CVVH (Continuous venovenous hemofiltration)
  • Convection
• CVVHD (Continuous venovenous hemodialysis)
  • Diffusion
• CVVHDF (Continuous venovenous hemodiafiltration)
  • Combination of convection and diffusion

References

Tandukar S, Palevsky PM. Continuous Renal Replacement Therapy: Who, When, Why, and How. Chest. 2019 Mar;155(3):626-638. doi: 10.1016/j.chest.2018.09.004. Epub 2018 Sep 25. PMID: 30266628; PMCID: PMC6435902.

Continuous Renal Replacement Therapy (CRRT) | Asahi Kasei Medical Co., Ltd. (n.d.). https://www.asahi-kasei.co.jp/medical/en/apheresis/product/crrt/about/cure.html

Cronin B, O'Brien EO. Intraoperative Renal Replacement Therapy: Practical Information for Anesthesiologists. J Cardiothorac Vasc Anesth. 2022 Aug;36(8 Pt A):2656-2668. doi: 10.1053/j.jvca.2021.10.002. Epub 2021 Oct 8. PMID: 34750060.